Various machines have been devised for the melting and spinning of meltable materials, especially sugar. The meltable material is introduced into a spinning head of a spinning machine in solid form. The material is melted therein just prior to be spun out from the spinner head where it solidifies in the air. The process of melt spinning sugar is most commonly seen in the manufacture of floss-like cotton candy.
Numerous machines have been specifically designed for melt spinning cotton candy. Examples of such machines are shown in U.S. Pat. Nos. 3,930,043, 3,073,262 and 3,070,045. These cotton candy forming spinning machines generally include a spinner head having a cylindrical apertured wall. Sugar in solid form is introduced into the spinner head where it is melted. The spinning of the spinner head causes the melted sugar to be spun out through the apertures in the cylindrical wall where it solidifies into the floss-like structure referred to as cotton candy. The characteristic shape and consistency of the spun material are influenced by many factors. These factors include size and construction of the spinner head, size, arrangement and location of the apertures in the cylindrical wall, as well as the manner in which heat is applied to the spinner head.
While typical cotton candy machines serve adequately in converting granular sugar into floss-like cotton candy, these cotton candy spinner heads do not produce material with repeatable consistency and therefore their use is not entirely satisfactory for spinning other materials, or other materials in combination with sugar. The art has seen a need for commercial spinner heads which produce repeatedly reliable material consistency so that the melt spinning of sugar as well as other materials, sugar combined with other materials as well as non-saccharide materials both for use in foodstuffs and pharmaceuticals, may be reliably achieved. U.S. Pat. No. 4,855,326 describes a melt-spin process for production of materials having pharmacological properties. U.S. Pat. No. 5,011,532 concerns the melt-spin production of oleaginous substances.
The art has also seen other advances in the spinner head construction for the production of various materials. For instance, U.S. Pat. No. 5,427,811 discloses a method and apparatus for spinning thermal-flow materials. The apparatus described therein includes a rotatable spinner head having a helical heating cable defining an annular processing wall having spaces between the heating cable through which material is propelled as the spinner head is rotated. The apparatus described in the '811 patent subjects the material to thermal-flow melt spin processing referred to as "Flash flow". Other commonly assigned patents describing the Flash flow process include U.S. Pat. No. 5,447,423, U.S. Pat. No. 5,445,769, U.S. Pat. No. 5,236,734 and U.S. Pat. No. 5,238,696.
Another technique for processing material in a melt spin environment is to subject the material to "Liquiflash" processing where reduction of the feedstock material occurs under conditions of heat and pressure so that any resistance of the material to liquid flow, i.e., viscosity which impedes the propensity to form liquid droplets, is eliminated. A method of forming liquiflash material is described in commonly assigned pending U.S. patent application Ser. No. 08/330,412 filed Oct. 28, 1994, now U.S. Pat. No. 5,683,720.
The Liquiflash and Flash-flow processes may be employed with various feedstock materials, specifically various foodstuffs including saccharides and non-saccharides as well as pharmaceuticals and combinations thereof. One apparatus which has been developed which is particularly suitable for spinning various foodstuffs and pharmaceuticals is shown and described in commonly assigned U.S. Pat. No. 5,458,823 issued Oct. 17, 1995. This patent discloses a spinner head having a plurality of discrete, closely spaced elongate heating elements disposed between a base and a cover. Feedstock material which is introduced into the spinner head may be expelled through the spaces formed between the heating elements.
In order to more efficiently produce pharmaceutical products, the spinner head of the '823 patent discloses an annular housing assembly formed of heat conductive material which is positioned over the heating elements. The heating elements are therefore isolated from the feedstock material by the annular housing assembly. In order to permit expulsion of feedstock material form the spinner head, the wall of the annular housing includes a plurality of slot-like openings through which the material may be expelled. The spinner head of the '823 patent is especially useful in the manufacture of pharmaceutical material in that in order to prevent contamination of reformed product, the annular housing may be easily removed from the heating elements so as to permit thorough cleaning.
Spinner heads of the type currently available in the art, however, typically experience a condition known as "blow by" in which unmelted, and therefore, unprocessed feedstock is ejected through the openings in the processing wall. Blow by is undesirable since it reduces the overall efficiency of the spinner head, therefore, attempts have been made to minimize the levels of blow by. One way to control blow by is to reduce the size of the opening extending through the processing wall. However, if these openings are made too narrow, they may have a negative effect on the morphology of the melt spun material and the amount of material which can be processed therethrough. In addition, undersized openings are subject to clogging which increases the down time of the spinner head. An alternative blow by minimizing method has been to employ restriction rings which extend about the radial perimeter of the spinner head as described in U.S. Pat. No. 5,458,823. Restriction rings typically obstruct the path through which the material must flow thereby increasing the time in which the material is in contact with the heated processing wall. Accordingly, there is less chance for the feedstock to be expelled in an unprocessed state.
The use of restriction rings or the narrowing of the exit slots, however, present a new set of complications. Specifically, restriction rings tend to lead to the formation of stagnation points which create clogs and unwanted flow path obstructions. For example as shown in FIG. 1, spinner head assemblies especially those which fit over tubular heating coils have generally planar radial inner processing wall surfaces 2 against which the feedstock material 3 is forced. The radial inner surface of an outer restriction ring 4 is also typically a generally planar surface. The configuration of these surfaces results in material buildup which has a cone-like configuration forming stagnation points 5. The material buildup covers the inner surfaces of the processing wall, thereby reducing efficiency of the head. When the material buildups to a certain degree, the material can no longer pass through the processing wall. Accordingly, spinner heads of this type typically require a considerable amount of maintenance to keep them in working order.
In addition, spinner heads currently available are limited in the amount of material they can process due to the limited ability to transfer thermal energy to the feedstock material. The planar surfaces of the processing wall present a relatively small amount of heated surface per unit area of the processing wall. Therefore, the ability of the processing wall to transfer heat to the feedstock is limited. Furthermore, since the material must be heated to processing temperature quickly after hitting the planar surface, these designs do not effectively process temperature sensitive materials which require a more gradual heating process.
Accordingly, it would be desirable to provide a spinner head for producing melt spun material that reduces the amount of feedstock blow by while reducing the formation of clog forming stagnation points. It would be further desirable to provide a spinner head for producing melt spun material which has increased processing wall surface area to increase the processing output of the spinner head.